if you're saying your upload speed is 2500
then you should never use more than 70-80% of your upload speed for streaming
(depends on the game you're playing etc whether it requires more bandwidth i.e mutiplayer gaming etc)
Suggest trying 2000 , then bring it down by a 100 until you find a sweet spot.
Use this to test the stability of your connection for streaming
You can improve performance by lowering your output resolution and frame rate, with an estimated maximum 1280x720 30fps at 1250kbps. Its much more viewable with a lower frame rate and higher quality image than trying run 60 frames per second at the same resolution. Keeping your canvas size at 1920x1080 can help maintain some of the detail on the lower quality 1280x720 output image. If you have an NVidia card on this list, be sure to set your encoding to nvenc for GTX or nvenc (new) for RTX: